U.S. patent number 9,381,117 [Application Number 13/142,416] was granted by the patent office on 2016-07-05 for medical knife.
This patent grant is currently assigned to MANI, Inc.. The grantee listed for this patent is Masahiko Saito. Invention is credited to Masahiko Saito.
United States Patent |
9,381,117 |
Saito |
July 5, 2016 |
Medical knife
Abstract
Provided is a medical knife which makes it possible to maintain
low penetration resistance, without the maximum-width parts of the
medical knife creating sudden changes in penetration resistance
even when passing through tissue. A knife comprises: a pointed tip;
a cutting part which has edges consisting of first oblique faces
which are formed along the outer periphery and second oblique faces
which are formed inside the first oblique faces; maximum-width
parts; and a shank part which is formed contiguously with the
maximum-width parts. The cutting part is formed in such a way that
the shape of the planar projection thereof becomes wider from the
pointed tip towards the maximum-width parts, and the first oblique
faces extend further towards the shank part side than the second
oblique faces over at least one portion of the area running from
the maximum-width parts to the shank part.
Inventors: |
Saito; Masahiko (Utsunomiya,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Saito; Masahiko |
Utsunomiya |
N/A |
JP |
|
|
Assignee: |
MANI, Inc. (Utsunomiya,
Tochigi, JP)
|
Family
ID: |
42287656 |
Appl.
No.: |
13/142,416 |
Filed: |
December 22, 2009 |
PCT
Filed: |
December 22, 2009 |
PCT No.: |
PCT/JP2009/071269 |
371(c)(1),(2),(4) Date: |
June 27, 2011 |
PCT
Pub. No.: |
WO2010/074047 |
PCT
Pub. Date: |
July 01, 2010 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
|
US 20110270292 A1 |
Nov 3, 2011 |
|
Foreign Application Priority Data
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|
|
|
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Dec 26, 2008 [JP] |
|
|
2008-332307 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
17/3205 (20130101); A61B 17/3211 (20130101); A61B
17/3209 (20130101); A61F 9/0133 (20130101); A61B
2218/00 (20130101); A61F 9/00736 (20130101) |
Current International
Class: |
A61B
17/32 (20060101); A61B 17/3211 (20060101); A61F
9/013 (20060101); A61F 9/007 (20060101) |
Field of
Search: |
;606/184,185,133
;604/164,167 ;30/48,123.7 ;31/184,185,133 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
2001-238890 |
|
Sep 2001 |
|
JP |
|
2005-013379 |
|
Jan 2005 |
|
JP |
|
2005-103035 |
|
Apr 2005 |
|
JP |
|
4161026 |
|
Oct 2008 |
|
JP |
|
Other References
International Search Report for PCT/JP2009/071269, Apr. 6, 2010.
cited by applicant.
|
Primary Examiner: Szpira; Julie A
Attorney, Agent or Firm: Shlesinger, Arkwright & Garvey
LLP
Claims
The invention claimed is:
1. A medical knife, comprising: a sharp tip; a cutting part
including a first oblique face formed along an outer periphery, an
edge formed by the first oblique face, the first oblique face is
formed by a flat surface, and a second oblique face formed inside
the first oblique face, a maximum-width part formed continuously
and proximally from the cutting part; and a shank part formed
continuously and proximally from the maximum-width part, wherein a
planar projection shape of the cutting part is formed such that a
width dimension increases from a side of the sharp tip toward the
maximum-width part, wherein the first oblique face is formed on an
outer peripheral side of the second oblique face on a portion from
the cutting part through the maximum-width part to the shank part
and the first oblique face extends further toward a side of the
shank part than the second oblique face on at least a part of a
portion from the maximum-width part to the shank part side, and
wherein a substantially triangular wedge-shaped surface is formed
on the maximum-width part of a side of the medical knife such that
an area of the substantially triangular wedge-shaped surface
increases from the cutting part to the shank, wherein the cutting
part includes a lower oblique face formed on a lower side of the
first oblique face, and the edge is formed by the first oblique
face formed on an upper side and the lower oblique face formed on
the lower side intersecting with each other along the outer
periphery forming an intersection, wherein the substantially
triangular wedge-shaped surface is defined by the edge of the first
oblique face and an edge of a lower oblique face, wherein the
intersection of the edges defines an apex and wherein the first
oblique face is formed such that the first oblique face lies on the
second oblique face at least at a part of the portion from the
maximum-width part to the shank part side.
2. The medical knife according to claim 1, wherein the first
oblique face and the lower oblique face are formed as ground
surfaces of which smoothness is higher than the smoothness of the
second oblique face.
Description
TECHNICAL FIELD
The present invention relates to a medical knife capable of making
an incision with small penetration resistance, which does not
generate drastic change in the penetration resistance even when a
maximum-width part passes, when incising an affected area.
BACKGROUND ART
In a cataract operation, a cornea and a sclera are incised with a
width corresponding to a dimension of a lens to be embedded for
embedding the lens in an eyeball. As the medical knife used when
incising the eyeball, there is one of which planar shape is formed
into a substantially rhombic shape. Such medical knife has a sharp
tip, a cutting part having two edges radially formed from the tip,
a maximum-width part in which a width dimension of the cutting part
is the largest, and a shank part continuously formed from the
maximum-width part of which width dimension decreases as is away
from the maximum-width part (for example, refer to Patent Document
1).
In a case of the above-described medical knife, by allowing the
same to straightly penetrate the eyeball, an incision corresponding
to the dimension of the maximum-width part may be formed.
Especially, in the medical knife disclosed in Patent Document 1,
durability of the sharp tip may be improved, and since the edges
are formed on both sides from the maximum-width part to the shank
part, the penetration resistance may be made small.
In the medical knife disclosed in Patent Document 1, the edges are
formed on the both sides in the maximum-width part and the edges
are formed also from the maximum-width part to the shank part.
Therefore, high incision performance to the tissue is maintained of
course from the tip to the maximum-width part and even after the
maximum-width part passes through the tissue.
Therefore, the penetration resistance generated when incising the
eyeball with the above-described medical knife is a substantially
similar small value from the tip to the maximum-width part and the
substantially similar penetration resistance is maintained even
after the maximum-width part passes through the tissue. When the
maximum-width part passes through the tissue and the width of the
knife decreases toward the shank, the penetration resistance
drastically decreases.
Patent Document 1: Japanese Patent No. 4161026
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
When incising the eyeball with the medical knife, a part with the
largest resistance is the cornea and the sclera, and the resistance
in a crystal lens is small. That is to say, when performing
incision operation by allowing the sharp tip of the medical knife
to face the tissue, the penetration resistance drastically
increases to achieve the largest value at a stage in which the tip
penetrates the tissue to form the initial incision. Thereafter, the
penetration resistance is generated also when the edge continuous
from the sharp tip expands the tissue. Then, after the
maximum-width part passes through the tissue, the penetration
resistance decreases. In this manner, when making an incision with
the medical knife, the penetration resistance changes in accordance
with progress in incision.
The change in the penetration resistance is preferably small. For
example, when the change between the penetration resistance when
forming the initial incision to the tissue and the penetration
resistance when expanding the initial incision is drastic and
large, since a doctor handles the medical knife by applying force
necessary to form the initial incision, excessive force acts on the
tissue from a moment that the initial incision is formed and a
penetration speed might increase to cause excessive incision. Also,
when the maximum-width part of the medical knife passes through the
tissue, when the change between the penetration resistance when
expanding the initial incision and the penetration resistance after
the maximum-width part passes through the tissue is drastic and
large, since the doctor handles the medical knife by applying force
necessary to expand the tissue, the excessive force acts on the
tissue from a moment that the maximum-width part passes through the
tissue and the penetration speed might increase to cause the
excessive incision.
Therefore, it is required that the doctor who handles the medical
knife sensitively responds to slight change in the penetration
resistance sensed by hand and finger, so that delicate handling and
sensitive sense are required for recognizing the change in the
penetration resistance, and there is a problem of fatigue in an
operation.
An object of the present invention is to provide the medical knife
capable of maintaining the small penetration resistance, not
generating the drastic change in the penetration resistance even
when the maximum-width part passes through the tissue, and
improving handleability.
Means for Solving Problem
In order to solve the above-described problem, the medical knife
according to the present invention includes a sharp tip, a cutting
part including an edge formed of a first oblique face formed along
an outer'periphery and a second oblique face formed inside the
first oblique face, a maximum-width part formed continuously from
the cutting part, and a shank part formed continuously from the
maximum-width part, wherein a planar projection shape of the
cutting part is formed such that a width dimension increases from a
side of the sharp tip toward the maximum-width part, and the first
oblique face extends further toward a side of the shank part than
the second oblique face on at least a part of a portion from the
maximum-width part to the shank part side.
Effect of the Invention
In the above-described medical knife (hereinafter, simply referred
to as the "knife"), the penetration resistance generated when
incising the tissue may be maintained small and the penetration
resistance does not drastically change even when the maximum-width
part passes through the tissue. Therefore, the doctor may make
weight on sensitivity to application of the force small when
handling to reduce the fatigue.
That is to say, in the knife of the present invention, in the
planar shape (planar projection shape), the width dimension
increases from the sharp tip to the maximum-width part and the
shank part is formed continuously from the maximum-width part.
Also, the cutting part has the edge formed of the first oblique
face and the second oblique face formed inside the first oblique
face. The first oblique face extends further toward the shank part
side than the second oblique face on at least a part of the portion
from the maximum-width part to the shank part.
In the knife of the present invention configured as above, in the
planar shape in the maximum-width part, the first oblique face to
form the edge obliquely intersects with the maximum-width part of
the knife and the first oblique face is formed along an outer
periphery of the maximum-width part to the shank part side.
Therefore, a substantially triangular wedge-shaped surface having
an intersection with the edge as an apex and is defined by an end
edge of the first oblique face and an end edge of a lower oblique
face of which area increases from the edge side toward the shank
part side is formed on a side surface of the knife.
Also, since the first oblique face is formed so as to lie on the
second oblique face on at least a part of the portion from the
maximum-width part to the shank part side, when it is configured
such that the width dimension gradually decreases from the
maximum-width part toward the shank part, a cross-sectional area
from the maximum-width part on which the first and second oblique
faces are formed to the shank part side may be made substantially
constant.
Therefore, the knife of the present invention may maintain the
penetration resistance small because the edge is formed on the
portion from the sharp tip to the maximum-width part, and may
maintain the small penetration resistance after forming the initial
incision to the tissue to the maximum-width part because the edges
are formed on the both sides of the maximum-width part.
After the maximum-width part of the knife passes through the tissue
by further handling of the knife, the edges are not formed on the
both sides of the knife, so that the penetration resistance larger
than the penetration resistance generated when the edge passes
through the tissue is generated. At that time, since a shape of the
side surface of the maximum-width part of the knife is the
substantially wedge-shape, this acts in a direction in which the
penetration resistance increases together with increase in the
penetration, on the other hand, the first oblique face is formed so
as to be overlapped with the second oblique face at least a part of
the portion from the maximum-width part to the shank part side and
the width dimension decreases, and this acts in the direction in
which the penetration resistance decreases, so that the generated
penetration resistance becomes substantially constant in the
vicinity of the maximum-width part. At the same time, after the
maximum-width part passes through the tissue, the width of the
knife decreases, so that this decreases together with this.
Therefore, the penetration resistance is continuously generated
also after the maximum-width part of the knife passes through the
tissue and the doctor is not affected by the drastic change in the
penetration resistance. Therefore, the doctor may recognize the
change in the penetration resistance while handling the knife,
thereby recognizing that the incision of the tissue is completed.
Also, since the drastic change in the penetration resistance is not
generated, there is a little possibility of forming the excessive
incision due to too much force applied when the maximum-width part
passes and it is possible to make the weight on the sensitivity to
the application of the force small.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an orthographic view of a knife according to this
embodiment.
FIG. 2 is a perspective view of the knife.
FIG. 3 is plan views of knives of comparative examples A to D, F
and G and the knife of the present invention E.
FIG. 4 is views illustrating measured values of penetration
resistance by the knives of the comparative examples A to D, F and
G and the knife of the present invention E.
DESCRIPTION OF LETTERS OR NUMERALS
A knife
1 cutting part
2 maximum-width part
3 shank part
4 tip
5 edge
6 first oblique face
7 lower oblique face
8 second oblique face
9 upper flat surface
6a, 8a boundary line
10 lower flat surface
11 side surface
BEST MODE(S) FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a medical knife according to
the present invention is described with reference to the drawings.
FIG. 1 is an orthographic view of the knife according to this
embodiment. FIG. 2 is a perspective view of the knife.
The knife according to the present invention has a function to
penetrate a tissue of an eyeball and the like to form an initial
incision and make an incision in a width direction from the initial
incision as a starting point to expand the same in a thickness
direction. Especially, it is configured such that drastic
difference is not generated between penetration resistance
generated when the knife penetrates the tissue to incise and the
penetration resistance just after a maximum-width part of the knife
passes through the tissue.
A material to form the knife according to the present invention is
not especially limited, and steels such as stainless steel and
carbon steel may be used. However, in view of an antirust property
and easier working, the stainless steel is preferably used and
among others, austenitic stainless steel is desirably used.
When the austenitic stainless steel is used as the material, it is
preferable to apply cold plastic working at a predetermined working
rate to extend a structure in a fiber shape and apply press
working, polish working and another necessary working while
maintaining the fiber-shaped structure in order to increase
hardness of the material.
In FIGS. 1 and 2, a knife A is composed of a cutting part 1, a
maximum-width part 2 on a widest position of the cutting part 1,
and a shank part 3 formed continuously from the maximum-width part
2. A tip of the cutting part 1 is formed as a sharp tip 4 and edges
5 are formed on both sides from the tip 4 as the starting point
toward the maximum-width parts 2. Also, it is formed such that a
width dimension gradually decreases from the maximum-width part 2
toward the shank part 3. Therefore, a planar shape (planar
projection shape) from the cutting part 1 through the maximum-width
part 2 to the shank part 3 of the knife A is formed into a
substantially rhombic shape.
Detailed dimensions such as a length dimension from the tip 4 to
the maximum-width part 2 and the width dimension of the
maximum-width part 2 are variously set according to an object of
the knife A, for example, a specification such as a dimension of
the incision.
Also, the planar shape of the maximum-width part 2 is not
especially limited, the knife A may have a rhombic planar shape
with the maximum-width parts 2 as apices and the maximum-width part
2 may be slightly linearly formed in a longitudinal direction of
the knife A.
The edge 5 is formed along an outer periphery of the cutting part
1. The edge 5 has a function to incise the tissue including a
cornea and a sclera and is formed of first oblique face 6 formed on
an upper side of a plane including two edges 5 formed on the both
sides from the tip 4 to the maximum-width part 2 as a boundary and
a lower oblique face 7 formed on a lower side thereof intersecting
with each other. In this manner, since the first oblique face 6 and
the lower oblique face 7 form the edge 5 together, the oblique
faces 6 and 7 are formed as ground surfaces with high
smoothness.
A second oblique face 8 is formed inside the first oblique face 6
along the first oblique face 6 formed on the upper side of the edge
5 of the cutting part 1, and a boundary line 6a is formed on a
boundary between the both oblique faces 6 and 8. Since the second
oblique face 8 does not have a function to form the edge 5, it is
not necessarily required to form the same of the ground surface
with the high smoothness and this may be a pressed surface or a
roughly ground surface. Also, an upper flat surface 9 is formed
along the second oblique face 8 and the upper flat surface 9 also
may be the pressed surface or the roughly ground surface as the
second oblique face 8.
A lower flat surface 10 is formed continuously from the lower
oblique face 7 formed on the lower side of the edge 5 of the
cutting part 1. Since the lower flat surface 10 is formed as a
surface, which does not have the function to form the edge 5, it is
not necessarily required to form the same of the ground surface
with the high smoothness and this may be formed as the roughly
ground surface or the pressed surface.
In the cutting part 1, the first oblique face 6 is formed of a flat
surface and this is formed to have the same width (dimension from
the edge 5 to the boundary line 6a) from the tip 4 to the vicinity
of the maximum-width part 2. The lower oblique face 7 formed on the
lower side of the plane including the two edges 5 also is formed as
the flat surface. Therefore, the edge 5 has a pointed sharp shape
by intersection of the two flat surfaces. In such cutting part 1,
the boundary line 6a being the boundary between the first oblique
face 6 and the second oblique face 8 is formed as a well-defined
ridge.
The above-described first oblique face 6 and lower oblique face 7
may be formed by using a grinding material having high flatness and
moderate rigidity. As such grinding material, there are a
grindstone, a belt-shaped grindstone of which rear surface is
supported by a highly rigid frame and the like, and they may be
selectively used.
The second oblique face 8 is formed inside the first oblique face 6
along the first oblique face 6. The second oblique face 8 is formed
such that an angle relative to the plane including the two edges 5
is smaller than an angle of the first oblique face 6. The second
oblique face 8 is substantially linearly formed along the first
oblique face 6 through the maximum-width part 2 to a side surface
to reach the shank part 3. Thus, a boundary line 8a being a
boundary between the second oblique face 8 and the upper flat
surface 9 is formed as a well-defined linear ridge.
The two edges 5 are formed from the tip 4 as the starting point,
the first oblique faces 6 are formed along the edges 5, and further
the second oblique faces 8 are formed inside the first oblique
faces 6 along the same, so that a line 6b on which the two first
oblique faces 6 intersect with each other and a line 8b on which
the two second oblique faces 8 intersect with each other become
continuous straight lines beginning from the tip 4.
The first oblique face 6 extends further toward a shank part 3 side
than the second oblique face at least a part of a portion from the
maximum-width part 2 to the shank part 3 side. In this embodiment,
the first oblique face 6 is formed on an outer peripheral side of
the second oblique face 8 on a portion from the cutting part 1
through the maximum-width part 2 to the shank 3 of the knife A.
Therefore, the first oblique face 6 extends further toward the
shank part 3 side than the second oblique face 8 on the portion
from the maximum-width part 2 to the shank part 3. However, it is
not required that the first oblique face 6 is formed over an entire
length of the second oblique face 8 formed from the maximum-width
part 2 to the shank part 3 and this may be formed on a part
thereof.
As described above, the knife A is such that the first oblique face
6, the second oblique face 8, and the upper flat surface 9 are
formed on the upper side of the plane including the two edges 5 of
the cutting part 1, and the lower oblique face 7 and the lower flat
surface 10 are formed on the lower side thereof. Therefore, as a
shape in a side view of the knife A, the edge 5, the ridge 6a, the
upper flat surface 9, and the lower flat surface 10 are represented
in a part corresponding to the cutting part 1.
Also, in a side view of the vicinity of the maximum-width part 2 of
the knife A, a point on which the edge 5 intersects with the
maximum-width part 2 is made an apex, the first oblique face 6 and
the lower oblique face 7 form two sides away from each other toward
the shank part 3 side, and a triangle-shaped side surface 11 by a
line on which the first oblique face 6 intersects with the upper
flat surface 9 and a line on which the lower oblique face 7
intersects with the lower flat surface 10 is formed.
On the side surface 11, a corner on the lower side forms an obtuse
ridge formed by intersection of the lower oblique face 7, and a
corner on the upper side forms an obtuse ridge 11a formed by
intersection of the first oblique face 6. Especially, an angle
formed by the ridge 11a on the upper side of the side surface 11
(angle between the first oblique face 6 and the side surface 11)
becomes larger than the angle formed when the second oblique face 8
directly intersects with the side surface 11, and it is possible to
significantly decrease the function to incise the tissue. That is
to say, the first oblique face 6 further chamfers a corner portion
on which the side surface 11 and the second oblique face 8
intersect with each other, and the ridge 11a on the upper side of
the side surface 11 is formed with the large angle.
In this manner, the first oblique face 6 further extending further
toward the shank part 3 side than the second oblique face 8 from
the maximum-width part 2 to the shank part 3 does not intersect
with the lower oblique face 7 but intersects with the side surface
11. Therefore, the edge is not formed on an outer peripheral
portion of the first oblique face 6 extending from the
maximum-width part 2 to the shank part 3 side.
The knife A composed as above has an excellent incision performance
to the tissue by the sharp tip 4 and the edge 5 in the cutting part
1 from the tip 4 to the maximum-width part 2 and is able to
decrease the penetration resistance when incising the tissue. Also,
the maximum-width part 2 has the incision performance only on an
apex portion on which the edge intersects with the side surface 11.
However, the edge 5 disappears at the same time as passing through
the maximum-width part 2, and further a thickness of the both end
portions in the width direction of the knife A increases together
with the triangle on the side surface 11, so that resistance
(frictional resistance) to expand an incision site is generated
when passing through the tissue. Further, since the width dimension
of the knife A decreases at the same time as passing through the
maximum-width part 2, the side surface 11 is separated from the
tissue and the resistance when passing through the tissue
decreases.
Therefore, until the maximum-width part 2 of the knife A passes
through the tissue, the resistance when the edge 5 incises the
tissue is generated as the penetration resistance, and soon after
the maximum-width part 2 passes through the tissue, difference
between the resistance generated when expanding the tissue and
decrease in the resistance by separation of the side surface 11
from the tissue is generated on the maximum-width part as the
penetration resistance. That is to say, after the maximum-width
part 2 of the knife A passes through the tissue, the penetration
resistance does not drastically decrease but gradually changes.
Therefore, a doctor may easily recognize that the maximum-width
part 2 passes through the tissue and may surely handle with
modulation.
Next, a process to manufacture the knife A in which the first
oblique face 6 extends further toward the shank part 3 side than
the second oblique face 2 in at least a part of the portion from
the maximum-width part 2 to the shank 3 side as described above is
simply described.
First, a material corresponding to the planar shape of a
destination knife A is formed. In this case, when the material is
the steel or martensite stainless steel, it is sufficient to cut
out a flat plate with the thickness of the knife A into the rhombic
shape by pressing. Also, when the material is the austenitic
stainless steel and the like, the press working may be applied to a
line material having the structure to which cold withdrawing
working is applied in advance to be extended in the fiber shape to
form the same into a rhombic flat plate shape.
The second oblique face 8 is formed on the rhombic material formed
in the above-described manner by pressing or grinding, and
thereafter, by forming the first oblique face 6 on a portion from
the tip 4 through the maximum-width part 2 to the shank part 3 side
by grinding the outer peripheral side of the second oblique face 8,
it is possible to extend the first oblique face 6 further toward
the shank part 3 side than the second oblique face on at least a
part of the portion from the maximum-width part 2 to the shank part
3 side.
Then, the knife A may be manufactured through another process
including a predetermined polishing process after forming the lower
oblique face 7.
When forming the first oblique face 6 on the rhombic material, by
grinding along the edge 5 and thereafter grinding along the side
surface 11 from the maximum-width part 2 to the shank part 3 side
by changing an attitude of the material, it is possible to extend
the first oblique face further toward the shank part 3 side than
the second oblique face on a part of the portion from the
maximum-width part 2 to the shank part 3 side.
However, it is preferable to continuously perform the grinding
along the edge 5 and the grinding along the side surface 11 without
performing such grinding in two steps. In this case, the attitude
of the material may be continuously changed according to the
grinding corresponding to the edge 5 and the grinding corresponding
to the side surface 11. When performing such grinding, in the
vicinity of the maximum-width part 2 of the knife A, the boundary
line 6a between the first oblique face 6 and the second oblique
face 8 becomes a curved-line shape and the width of the first
oblique face 6 (dimension from the edge 5 to the boundary line 6a
and dimension from the side surface 11 to the boundary line 6a)
increases.
It is also possible to form the first oblique face 6 in a precedent
process and form the second oblique face 8 in a successive
process.
Next, a result of comparing the penetration resistance of the knife
A according to the present invention and the penetration resistance
of a knife according to a comparative example is described. FIG. 3
are plan views of knives of comparative examples A to D, F and G
and the knife of the present invention E. FIG. 4 are views
illustrating measured values of the penetration resistance by the
knives of the comparative examples A to D, F and G and the knife of
the present invention E.
Meanwhile, an experiment to measure the penetration resistance was
performed by allowing the knife to be tested to vertically
penetrate the sclera of a swine eye cut to have a thickness of 400
.mu.m to 450 .mu.m as a material to be penetrated and measuring the
resistance by a load cell. The penetration was performed three
times for each of three tests.
In FIGS. 3 and 4, in the knife of the comparative example A, the
edge in a gradual curved-line shape is formed from the sharp tip
through the maximum-width part to the shank part side.
In the knife of the comparative example A, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 160 mN
(millinewton, the same shall apply hereinafter) to approximately 95
mN. Also, the penetration resistance relatively monotonously
decreases after forming the initial incision and drastically
decreases just before a lapse of 2 seconds (time at which the
maximum-width part passes through the material to be penetrated).
In this case, since the penetration resistance is small, it may be
said that this has the excellent incision performance.
In the knife of the comparative example A, the tip is sharp and the
edge is formed through the maximum-width part to the shank part
side, so that the penetration resistance is small and this has the
excellent incision performance. However, variation in measured
values is large, the penetration resistance monotonously decreases,
and a change rate is large. Therefore, it might be difficult for
the doctor to clearly recognize a time point at which the
maximum-width part passes through the tissue.
In the knife of the comparative example B, a substantially linear
edge is formed from the sharp tip to the maximum-width part, the
edge is not formed from the maximum-width part to the shank part
side, and the width dimension linearly decreases.
In the knife of the comparative example B, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 300 mN to
approximately 190 mN. The penetration resistance drastically
decreases after forming the initial incision to be maintained at a
substantially constant value and drastically decreases just before
the lapse of 2 seconds. Especially, the substantially constant
penetration resistance when penetrating the material to be
penetrated is within a range from approximately 220 mN to
approximately 140 mN.
In the knife of the comparative example B, the penetration
resistance is large, and the incision performance thereof is poor.
Also, the change in the penetration resistance just before the
lapse of 2 seconds is large and it might be difficult for the
doctor to recognize that the maximum-width part of the knife passes
through the tissue when incising the same.
In the knife of the comparative example C, the edge in the gradual
curved-line shape is formed from the sharp tip to the maximum-width
part, the edge is not formed from the maximum-width part to the
shank part and the width linearly decreases.
In the knife of the comparative example C, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 210 mN to
approximately 110 mN. The change in the penetration resistance
gradually decreases after forming the initial incision and
relatively drastically decreases just before the lapse of 2
seconds.
In the knife of the comparative example C, the penetration
resistance is not especially large but is not a small value. Also,
the change just before the lapse of 2 seconds is large. Therefore,
it might be difficult for the doctor to recognize that the
maximum-width part of the knife passes.
In the knife of the comparative example D, the edge is
substantially linearly formed from the sharp tip to the
maximum-width part, the width gradually decreases from the
maximum-width part to the shank part, and thereafter, the width
decreases in a curved-line shape convex inward.
In the knife of the comparative example D, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 180 mN to
approximately 120 mN. The change in the penetration resistance is
small and after forming the initial incision to the tissue, the
penetration resistance is substantially constant and drastically
decreases just before the lapse of 2 seconds.
In the knife of the comparative example D, the penetration
resistance is not especially large but is not a small value.
Especially, since the penetration resistance after forming the
initial incision to the material to be penetrated is substantially
constant, the change just before the lapse of 2 seconds is
extremely large. Therefore, it might be difficult for the doctor to
recognize that the maximum-width part of the knife passes.
The knife A according to the present invention is illustrated in E.
In this knife A, the penetration resistance when forming the
initial incision to the material to be penetrated is within a range
from approximately 100 mN to approximately 60 mN. Also, after
forming the initial incision, the penetration resistance slightly
decreases but the change is not large. This relatively gradually
decreases just before the lapse of 2 seconds.
In the knife A according to the present invention (E), the
penetration resistance is small, the change after forming the
initial incision is small, and further, the change just before the
lapse of 2 seconds is gradual. Therefore, the doctor may decrease
the force when allowing the knife to pass through the tissue, and
it is also possible to make an incision by applying constant force.
Further, the change in the penetration resistance when the
maximum-width part passes through the tissue also is gradual and
the doctor may easily recognize that the maximum-width part of the
knife passes through the tissue.
The knife of the comparative example F has a shape substantially
identical to that of the knife of the comparative example D. That
is to say, the knife of the comparative example F is such that the
edge is substantially linearly formed from the sharp tip to the
maximum-width part, the width gradually decreases from the
maximum-width part to the shank part, and thereafter, the width
decreases in the curved-line shape convex inward.
In the knife of the comparative example F, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 160 mN to
approximately 130 mN. The change in the penetration resistance is
small, the penetration resistance further increases after forming
the initial incision to the tissue and drastically decreases just
before the lapse of 2 seconds.
In the knife of the comparative example F, the penetration
resistance is not especially large but is not a small value.
Especially, after forming the initial incision to the material to
be penetrated, the penetration resistance increases and the change
just before the lapse of 2 seconds is extremely large. Therefore,
it might be difficult for the doctor to recognize that the
maximum-width part of the knife passes.
In the knife of the comparative example G, the edge is
substantially linearly formed from the sharp tip to the
maximum-width part, a length of the maximum-width part is
substantially identical to the length of the cutting part, the
width slightly decreases at the part toward the shank part, and
thereafter, the width decreases in the curved-line shape convex
inward.
In the knife of the comparative example G, the penetration
resistance when forming the initial incision to the material to be
penetrated is within a range from approximately 270 mN to
approximately 170 mN. The penetration resistance further increases
after forming the initial incision to the tissue and drastically
decreases just before the lapse of 2 seconds.
In the knife of the comparative example G, the penetration
resistance is especially large. Also, after forming the initial
incision to the material to be penetrated, the penetration
resistance increases and the change just before the lapse of 2
seconds is extremely large. Therefore, a load when the doctor
handles is large and it might be difficult to recognize that the
maximum-width part of the knife passes.
As in the above-described experimental result, in the knife A of
the present invention, a value of the largest penetration
resistance generated when forming the initial incision to the
material to be penetrated is 100 mN and is the smallest as compared
to that of other comparative examples. Therefore, the knife A of
the present invention is most excellent in the penetration
performance.
They are the knives of the comparative examples A and C and the
knife A of the present invention in which the change of the
penetration resistance just before the lapse of 2 seconds is small
(inclination of a change curve is gradual), and among others, the
change in the knife A of the present invention is the smallest.
Therefore, in the knife A of the present invention, when the doctor
handles the same by applying substantially identical force, even
when the maximum-width part of the knife A passes through the
tissue, excessive force is not applied to the tissue and there is
no possibility of forming an excessive incision.
As described above, in the knife A of the present invention, the
penetration resistance when forming the initial incision is small,
the change in the penetration resistance after forming the initial
incision until the maximum-width part passes therethrough is small,
and further, the penetration resistance is present also after the
maximum-width part passes. Therefore, the doctor may allow the
knife to pass through the tissue by applying small force and may
incise the tissue by substantially identical force. Then, since the
change in the penetration resistance is small also before and after
the maximum-width part passes through the tissue, there is a little
possibility of incising the tissue excessively also when the doctor
handles by applying the substantially identical force.
INDUSTRIAL APPLICABILITY
The knife according to the present invention has no possibility of
forming the excessive incision to the tissue when penetrating the
tissue to incise. Therefore, this may be utilized not only to an
operation on eye but also to an operation to make an incision while
maintaining the dimension of the incision constant.
* * * * *